This supplemental application is made to request further support for the previously funded research. The objective of the work is to study the mechanisms by which cells in the vertebrate retina detect and analyze light stimuli. At present, before proceeding to the interactions between higher order retinal neurons, it seems appropriate to study further the generation and transmission of neural signals at the level of the receptors. Using intracellular recording, studies will be made of the relation between the sensitivity of a receptor and the angle of incidence of the light falling on it. An examination will be made of possible transmitters released by receptors and by horizontal cells, and the way in which the release is regulated by presynaptic membrane potential. When these studies are completed, interactions between higher order retinal neurons will be approached, with the long range goal of obtaining a reasonably complete picture of the way in which the cells in the retina accomplish the tasks of signal detection and analysis.